Ion beam process for deposition of highly wear-resistant optical coatings

• US 5,888,593 A
• Filed: 04/12/1996
• Issued: 03/30/1999
• Est. Priority Date: 03/03/1994
• Status: Expired due to Term

• Current Assignee: Morgan Advanced Ceramics Inc.
• Original Assignee: Monsanto Company (Bayer AG)
• Inventors: Kimock, Fred Michael, Venable, Ray Hays III, Petrmichl, Rudolph Hugo, Mahoney, Leonard Joseph, Knapp, Bradley J., Galvin, Norman Donald
• Primary Examiner(s): PADGETT, MARIANNE L
• Application Number:
  US08/631,170
• Time in Patent Office: 1,082 Days
• Field of Search: 427/524, 427/525, 427/527, 427/529, 427/530, 427/562, 427/563, 427/574, 427/579, 427/577, 427/534, 427/573, 204/37, 204/192.35
• US Class Current: 427/563
• CPC Class Codes: C23C 16/0245 by etching with a plasma
• CPC Class Codes: C23C 16/30 Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
• CPC Class Codes: C23C 16/308 Oxynitrides
• CPC Class Codes: C23C 16/325 Silicon carbide
• CPC Class Codes: C23C 16/345 Silicon nitride
• CPC Class Codes: C23C 16/36 Carbonitrides
• CPC Class Codes: C23C 16/513 using plasma jets

Abstract

An ion beam deposition method is provided for manufacturing a coated substrate with improved wear-resistance, and improved lifetime. The substrate is first chemically cleaned to remove contaminants. Secondly, the substrate is inserted into a vacuum chamber onto a substrate holder, and the air therein is evacuated via pump. Then the substrate surface is bombarded with energetic ions from an ion beam source supplied from inert or reactive gas inlets to assist in removing residual hydrocarbons and surface oxides, and activating the surface. After sputter-etching the surface, a protective, wear-resistant coating is deposited by plasma ion beam deposition where a portion of the precursor gases are introduced into the ion beam downstream of the ion source, and hydrogen is introduced directly into the ion source plasma chamber. The plasma ion beam-deposited coating may contain one or more layers. Once the chosen coating thickness is achieved, deposition is terminated, vacuum chamber pressure is increased to atmospheric and the coated substrate products having wear-resistance greater than glass are removed from the chamber. These coated products may be ceramics, architectural glass, analytical instrument windows, automotive windshields, and laser bar code scanners for use in retail stores and supermarkets.

Claims

1. A method for producing an optically transparent coating on the exposed surface of a substrate comprising in sequence:

(a) chemically cleaning the surface of said substrate to remove residual hydrocarbons and other contaminants;

(b) mounting said substrate in a deposition vacuum chamber and evacuating the air from said chamber;

(c) sputter-etching the surface of said substrate with a beam of ions to further remove residual hydrocarbons and other surface contaminants, and to activate the surface;

(d) plasma ion beam depositing using silicon-containing precursor gases at least one layer of an amorphous material selected from the group consisting of a silicon oxide, silicon carbide, silicon nitride, silicon oxy-carbide, silicon oxy-carbonitride, and silicon oxy-nitride and using a gridless ion source having a plasma chamber therein, wherein a plasma is generated in the plasma chamber and wherein a gas stream containing at least a portion of said precursor gases is introduced outside of the ion source and into the plasma ion beam, and a gas stream containing hydrogen is introduced directly into said plasma chamber during the deposition;

(e) increasing the vacuum chamber pressure to atmospheric pressure; and

(f) recovering a coated substrate product with an abrasion resistance greater than the abrasion resistance of glass lenses.

2. The method of claim 1 wherein said silicon-containing precursor gases have a C/Si ratio less than 3.

3. The method of claim 1 wherein a temperature of said substrate during the deposition is about 200°

C. to about 500°

C.

4. The method of claim 1 wherein said ion beam has a beam current density at said substrate of greater than about 1.5 mA/cm² and has a mean beam kinetic energy in the range of about 20 eV to about 200 eV.

5. The method of claim 1 wherein said gridless ion source is selected from the group consisting of an End Hall ion source and a Hall accelerator ion source.

6. The method of claim 1 wherein said substrate comprises a material selected from the group consisting of a ceramic, a glass, and mixtures thereof.

7. The method of claim 1 wherein said abrasion-resistant coating includes multiple layers of at least two different refractive indices to reduce reflection at predetermined wavelengths.

8. The method of claim 1 wherein said substrate is an optically transparent material.

9. The method of claim 1 wherein said substrate is an optically transparent lens.

10. The method of claim 1 wherein said substrate is a bar code scanner window.

11. The method of claim 1 wherein said silicon-containing precursor gases are selected from the group consisting of silane, disilane, hexamethylcyclotrisilazane, tetramethylcyclotetrasiloxane, tetramethyldisiloxane, and tetramethyldisilazane.

12. The method of claim 1 wherein said silicon-containing precursor gases are selected from the group consisting of hexamethylcyclotrisilazane, tetramethylcyclotetrasiloxane, tetramethyldisiloxane, and tetramethyldisilazane.

13. A method for depositing onto a parent substrate an optically transparent coating material having at least one amorphous layer consisting of silicon oxy-nitride or silicon oxy-carbonitride which comprises in sequence:

(a) chemically cleaning the exposed surface of said substrate to remove residual hydrocarbons and other contaminants;

(b) mounting said substrate in a deposition vacuum chamber and evacuating the air from said chamber;

(c) sputter-etching the surface of said substrate with a beam of ions to further remove residual hydrocarbons and other surface contaminants, and to activate the surface;

(d) plasma ion beam depositing said amorphous layer onto the surface of said substrate by exposing said substrate to silicon-containing precursors selected from the group consisting of hexamethylcyclotrisilazane, tetramethylcyclotetrasiloxane, tetramethyldisiloxane, and tetramethyldisilazane, whereby said precursor gases are activated by said plasma ion beam and said substrate is bombarded by ions during deposition using a gridless ion source having a plasma chamber therein, wherein a plasma is generated in the plasma chamber and wherein a gas stream containing at least a portion of said precursor gases is introduced outside of the ion source and into the plasma ion beam, and a gas stream containing nitrogen and hydrogen is introduced directly into said plasma chamber during the deposition;

(e) increasing the vacuum chamber pressure to atmospheric pressure; and

(f) recovering a product having an abrasion resistance greater than the abrasion resistance of glass lenses, having a Vicker'"'"'s microindentation hardness of about 1200 kg/mm² to about 1700 kg/mm² and having optical transparency in the visible region with a minimum transmission of about 75% at 633 nm wavelength when said coating is deposited to a thickness of about 3 to about 6 micrometers.

14. The method of claim 13 wherein the gas stream fed directly into said plasma chamber also contains oxygen.

15. A method for depositing onto a parent substrate an optically transparent coating material having at least one amorphous layer consisting of silicon oxy-nitride or silicon oxy-carbonitride which comprises in sequence:

(a) chemically cleaning the exposed surface of said substrate to remove residual hydrocarbons and other contaminants;

(b) mounting said substrate in a deposition vacuum chamber and evacuating the air from said chamber;

(c) sputter-etching the surface of said substrate with a beam of ions to further remove residual hydrocarbons and other surface contaminants, and to activate the surface;

(d) plasma ion beam depositing said amorphous layer onto the surface of said substrate by exposing said substrate to silicon-containing precursors selected from the group consisting of hexamethylcyclotrisilazane, tetramethylcyclotetrasiloxane, tetramethyldisiloxane, and tetramethyldisilazane, whereby said precursor gases are activated by said plasma ion beam having a beam current density at said substrate of greater than about 1.5 mA/cm² and having a mean beam kinetic energy of about 20 to about 200 eV, and said substrate, at a temperature of about 200°

C. to about 500°

C., is bombarded by ions during the deposition using a gridless ion source having a plasma chamber therein, wherein a plasma is generated in the plasma chamber and wherein a gas stream containing at least a portion of said precursor gases is introduced outside of the ion source and into the plasma ion beam, and a gas stream containing nitrogen, hydrogen, oxygen is introduced directly into said plasma chamber during the deposition;

(e) increasing the vacuum chamber pressure to atmospheric pressure; and

(f) recovering a product having an abrasion resistance greater than the abrasion resistance of glass lenses, having a Vicker'"'"'s microindentation hardness of about 1200 to about 1700 kg/mm² and having optical transparency in the visible region with a minimum transmission of about 75% at 633 nm wavelength when said coating is deposited to a thickness of about 3 to about 6 micrometers.